How to Set Up a Mac WiFi Network with No Base Station
Most of the heavy lifting needed to set up a WiFi network takes place at the access point or base station. But if you just want to network with a bunch of other WiFi-equipped computers, you don’t need a base station.
Just select Create Network from the Wireless icon list. Give your network a name. Turn on WEP encryption if you like — that’s all Apple offers, so don’t use this mode for sensitive information. Your WiFi Network is ready.
Windows can do this trick, too, and you can join each other’s networks. Computer-to-computer networks like this one show up in a separate section of the Wireless icon list.